1. Field of the Invention
The present invention relates generally to communications networking, and more specifically, to filtering and forwarding frames in an optical network.
2. Related Art
In regards to communications networks, there is a continuous challenge to achieve an optimal balance among various network characteristics. Such characteristics include bandwidth demand and quality of service parameters, such as latency, loss, or priority. For example, data-over-cable networks presently are expanding the variety of services traditionally provided to subscribers. In addition to television broadcasts, cable providers are offering telephony, messaging, and Internet services. As a result, additional bandwidth is needed to support the timely delivery of these services. Moreover, traditional cable broadcasts primarily require one-way communication from a cable service provider to a subscriber's home. As interactive or personal television services and other nontraditional cable services continue to be offered, communications media used to support one-way communications must now contend with an increased demand for bi-directional communications.
Optical networks are evolving as a solution to bandwidth limitations prevalent on communication networks. For example, a passive optical network (PON) can be built to gain bandwidth efficiency and reduce protocol overhead. A typical PON consists of an optical line terminal (OLT) that manages communications with a plurality of optical network units (ONUs). Conventional PON topology has a shared upstream and a broadcast downstream. The ONUs have the opportunity to listen to the downstream broadcasts. However, the OLT uses time division multiplexing to enable the ONUs to send frames containing data and/or requests in assigned slots in the upstream. Frames sent in the upstream from one ONU are not seen by the other ONUs.
The communications path between an OLT and its ONUs is referred to as a PON segment. A conventional PON segment is neither a point-to-point (P2P) segment nor a shared segment. In a typical shared segment, a frame is seen by all attached devices. In a PON segment, however, frames on the upstream are not seen by any other device. When upstream frames arrive at the OLT from a PON segment, the frames are processed, filtered and forwarded to the next destination. The OLT uses a forwarding entity (such as, a bridge or router) to execute the filtering and forwarding operations. Conventional forwarding entities only support P2P or shared segments, and as discussed, conventional PON segments are neither. Therefore, conventional forwarding entities assume all devices linked to one of its ports have seen any frame delivered to that port. As a result, the forwarding entity will not send a frame back to the port that delivered the frame, even if a destination is an end user linked to the incoming PON segment.
Therefore, a method and system are needed to address the above problems.